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Response:

The "backwards" planets and moons are in no way contrary to the nebular
hypothesis. Part of the hypothesis is that the nebula of gas and dust
would accrete into planetessimals. Catastrophic collisions between
these would be part of planet building. Such collisions and other
natural processes can account for the retrograde planets and moons.

The only moons that orbit retrograde are small asteroid-sized distant
satellites of giant planets such as Jupiter and Saturn, plus Triton
(Neptune's large moon) and Charon (Pluto's satellite). The small
retrograde satellites of Jupiter and Saturn were probably asteroids
captured by the giant planets long after formation of the solar system.
It is actually easier to be captured into a retrograde orbit. The
Neptune system also contains one moon, Nereid, with a highly eccentric
orbit. It appears that some sort of violent capture event may have
taken place. The Pluto-Charon system is orbiting approximately "on its
side," technically retrograde, with tidally locked rotation. As these
are small bodies in the outer solar system, and binaries are likely to
have been formed through collisions or gravitational capture, this does
not violate the nebular hypothesis.

Uranus is rotating more or less perpendicular to the plane of the
ecliptic. This may be the result of an off-center collision between
two protoplanets during formation. Venus is rotating retrograde but
extremely slowly, with its axis almost exactly perpendicular to the
plane of its orbit. The rotation of this planet may well have started
out prograde, but solar and planetary tides acting on its dense
atmosphere have been shown to be a likely cause of the present state of
affairs. It is probably not a coincidence that at every inferior
conjunction, Venus turns the same side toward Earth, as Earth is the
planet that contributes most to tidal forces on Venus.

Orbital motions account for 99.9% of the angular momentum of the solar
system. A real evidential problem would be presented if some of the
planets orbited the sun in the opposite direction to others, or in very
different planes. However, all the planets orbit in the same
direction, confirming the nebular hypothesis, and nearly in the same
plane. A further confirmation comes from the composition of the giant
planets, which are similar to the sun's composition of hydrogen and
helium. Giant planets could hold on to all of their light elements,
but small planets like Earth and Mars could not.